The subject invention relates to a spray applied building construction coating material that forms a waterproofing, water resistant, water vapor permeable, air barrier, building wrap coating layer (i.e. a weather resistive barrier) between an exterior facing surface of a building sheathing layer and an interior facing surface of an exterior building cladding layer; to a spray applied building wrap; and to a building construction assembly formed by spray applying the coating material onto the sheathing, allowing the coating material to solidify to form a building wrap coating layer on the sheathing, and applying an exterior cladding layer over the building wrap coating layer. For many applications, it is preferable that the coating material solidify to form a building wrap coating layer with a textured exterior facing surface that provides passages between the exterior facing surface of the building wrap coating layer and an interior facing surface of the exterior cladding layer for draining water from between and permitting air flow between the exterior facing surface of the building wrap coating layer and the interior facing surface of the exterior cladding layer.
In current building construction weather resistive barriers providing some level of waterproofing, water vapor permeability, and air passage impedance (commonly referred to in the industry as building wraps) are frequently used between the exterior sheathing layer of the exterior wall and the exterior cladding layer of the exterior wall. The exterior sheathing layer is located on and secured the exterior side of the load-bearing framing members of the exterior wall. A major function of the building wrap is to prevent or minimize the intrusion of moisture into the exterior sheathing layer of the exterior wall, the framing members of the exterior wall, the insulation within the exterior wall, and the interior sheathing layer of the exterior wall. The exterior sheathing layer is normally formed of plywood, oriented strand board (OSB), foam insulation sheathing, nonwoven glass mat faced gypsum sheathing board, or other conventional sheathing materials commonly used in the construction industry and the exterior cladding layer is normally formed of brick, concrete blocks, reinforced concrete, stone, vinyl siding, fiber cement board, clapboard, or other conventional exterior siding materials commonly used in the construction industry. There are two basic forms of building wrap. The most common form of building wrap is a sheet building wrap and the less common form of building wrap is a spray applied building wrap.
Sheet building wraps are exemplified by Patent Application Publication No. US 2006/0040091 A1, Bletsos et al, published on Feb. 23, 2006 and Patent Application Publication No. US 2006/0051560 A1, McKenna et al, published on Mar. 9, 2006. Where moisture penetrates through the exterior cladding layer of an exterior wall to the building wrap layer, the presence of moisture on the surface of the building wrap layer can promote the growth of fungi and molds within the exterior wall. The building wrap of the McKenna et al patent application is embossed to form “drip channels or drainage channels” and promote moisture drainage from within an exterior wall to reduce the possibility of fungi or mold growth within an exterior wall due to the retention of moisture within the exterior wall. The utilization of these sheet building wraps as waterproofing, water vapor permeable, air barriers in exterior walls is not without its problems. The performance of the sheet building wrap layers formed by these sheet building wraps can be significantly degraded from any one or more of the following causes: the sheet building wraps of the sheet building wrap layer can become torn during application, adjacent sheet building wraps of the sheet building wrap layer can come apart at the seams between the sheets, and staples or other mechanical fasteners used to secure the sheet building wraps to the sheathing to form the sheet building wrap layer can create holes in the sheet building wraps that often enlarge, especially in windy conditions. In extreme weather conditions, large sections of the sheet building wraps often tear loose. To effectively form an air barrier, these sheet building wrap products must have all seams taped and the tops (roof side) and bottoms (foundation side) of the sheet products secured to the building with air sealing caulk, mastic, or tape. Without this level of detailed sealing the air barrier performance of the sheet building wrap layers formed with these sheet products is significantly less effective.
The ability of a building wrap to provide water drainage and an air wash is particularly important when the exterior cladding is a reservoir cladding (i.e. when it rains, the cladding gets wet and absorbs water). When the sun comes out after the rain has saturated the cladding, the heat of the sun drives some of the absorbed water out through the exterior side of the cladding, but the sun also drives a significant amount of the absorbed water into the cladding and out through the inner side of the cladding. This is especially common in porous cladding materials such as brick. Most cladding materials permit some amount of absorbed water to pass out through the inner side of the cladding material through various mechanisms. The two most common mechanisms functioning to pass water out through the inner side of the claddings are wind driven rain that penetrates through cracks and seams in the claddings and the claddings functioning as reservoirs.
Spray applied building wraps are exemplified by Sto Guard® spray applied building wrap marketed by Sto Corp. of Atlanta, Ga. and by Henry® Air-Bloc 31, Henry® Air-Bloc 33, and Henry® Blueskin® Breather marketed by Henry Company of Huntington Park, Calif. These spray applied building wraps are formed by spray applying a liquid that dries (solidifies) to form a waterproofing, water vapor permeable, air barrier coating layer, such as a liquid emulsion utilized by the Henry Company that solidifies into a rubberized (elastomeric) membrane. The use of spray applied building wraps rather than sheet building wraps to form a building wrap layer eliminates many of the problems associated with the use of sheet building wraps, such as those problems caused by sheet tears, seam separation, and fastener penetration and the formation of building wraps. In addition, the spray application of spray applied building wraps is relatively fast, easy, and does not require the use of highly skilled labor. However, these spray applied building wraps do not provide drip or drainage channels to promote moisture drainage from within an exterior wall to reduce the possibility of fungi or mold growth within an exterior wall due to the retention of moisture within the exterior wall.